For many years there have been products on the market which have guarded against nefarious reproduction of checks, motor vehicle titles, and like documents which the owner wishes to retain secure. For example products sold by Moore Business Forms, Inc. of Lake Forest, Illinois under the trademarks "HIDDEN WORD", and "MOOREGUARD.RTM.", and products such as shown in U.S. Pat. Nos. 4,582,346, 4,265,469, and 4,175,774 have been provided which are reasonably effective in preventing counterfeiting utilizing xerographic photocopiers, even many color copies such as the Xerox L-6500. However, photocopy machine technology has increased substantially, and now there are many copiers out on the market that have higher resolution than in the past, and provide copies utilizing processes other than the xerographic process, such as by laser copying. One such photocopy machine is a Canon 500 color copier, which has high resolution and which uses laser technology rather than xerographic technology. Prior art protected documents (also known as security documents) are not effective in preventing nefarious reproduction of documents utilizing copiers such as the Canon 500 color copier if the operator is able to change copier settings. Utilizing such equipment, a setting can almost always be found which allows accurate counterfeiting of ostensibly protected documents.
According to the present invention, a protected document, and a method of producing a document so that it is not reproduced accurately, are provided which are effective even with the modern resolution copiers, and those utilizing non-xerographic technologies, such as the Canon 500 color copier. The document according to the invention is able to provide a warning word or symbol upon reproduction because it utilizes different screen densities (that is dot/rule thicknesses) so that even if a would be counterfeiter can adjust the settings of the copier, no setting can be found which accurately reproduces the entire protected document, that is without a warning word or symbol being visible by the human naked eye.
According to one aspect of the present invention, a protected document is provided comprising the following elements: A substrate having a surface. At least three discrete halftone printed bands disposed on the surface and provided by geometric elements. Each of the printed bands having a significantly different screen density than proximate bands. Within each band the geometric elements comprising a warning word or symbol, and a background. And, within each band, one of the warning word or symbol and background having geometric elements of a size such that they are readily reproduced by a photocopy machine, while the other of the warning word or symbol and background has geometric elements of a size such that they are not readily reproduced by a photocopy machine.
The variety of individual components of the protected document according to the present invention is enormous. For example, the geometric elements may comprise dots (e.g. circular or non-circular dots), lines, or other elements; and the size of the geometric elements that are readily reproduceable are typically about 24-34 per centimeter, while those that are not readily reproduceable are about 52-64 per centimeter, regardless of density.
The bands on the protected document are typically provided in sequence, for example they can be either linear bands or circular bands. The screen densities of the discrete bands are about 1%-10% different than the screen densities of an adjacent band, depending upon color. The densities of the bands for light inks, such as greens, range from about 1-45%, while the density of bands for very light inks, such as yellows, range from about 1 to 80%, and the densities of dark inks, such as blues, blacks, and some reds, range from about 1-35%. The bands typically cover substantially the entire substrate surface, and it is preferred to use interband areas having densities gradually transitioning between the densities of adjacent bands. Normally the total density variation between discrete bands is about 10-25%, but again that will depend upon ink color and the size of the document. Most of the time all of the geometric elements will be of the same color, however geometric elements of different color may also be utilized.
The warning word or symbol may be any easily recognized word or symbol, such as the word "Void". Normally the geometric elements making up the "Void" are what drop out upon photocopying, although the background may drop out instead. Where a plurality of adjacent bands are provided, normally a uniform progression in density from darker to lighter, or lighter to darker (or both) is provided. The substrate may also include other indicia, such as full tone indicia in the form of monetary or control number indicia, and a camouflage background may also be provided.
The document according to the invention is the only known document which cannot be accurately reproduced (that is with the "Void" or like warning symbol becoming visible to the naked eye) by one utilizing a Canon 500 color copier having access to setting changes.
According to another aspect of the present invention, a method of producing a document on a photocopy machine is provided. The method comprises the following steps: (a) Producing a document from a substrate having a surface by printing at least three discrete halftone bands comprising ink geometric elements on the surface, so that each of the printed bands has a different screen density, and within each band there is printed a halftone indica, and a background, and within each band, one of the halftone indicia and background has geometric elements of a size such that they are reproduced by a photocopy machine, while the other of the halftone indicia and background has geometric elements of a size such that they are not reproduced by a photocopy machine. (b) Printing full tone indicia on the surface which is accurately reproducible by a photocopy machine. And, (c), reproducing the document on a photocopy machine, so that regardless of the setting of the photocopy machine at least one band of halftone indicia or associated background geometric elements do not reproduce accurately as viewed by the naked human eye; while the full tone indicia and the halftone indicia or associated background geometric elements which do reproduce accurately, are accurately reproduced. As indicated above, the document produced utilizing the method as recited above, even if reproduced on a laser copier, such as a Canon 500 color copier, will indicate the warning word or symbol in at least one of the bands thereof since it is impossible to adjust the copier to accurately reproduce all the bands of varying densities.
It is the primary object of the present invention to provide a protected document which will not accurately reproduce on any type of photocopy machine, but rather will indicate a warning. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.